1. Field of the Invention
The present invention relates to a method for driving a servo-motor, and more particularly to a new improvement for detecting power voltage without using a current feedback loop, comprising a current sensor and an A/D converter, which is conventionally used for detecting motor current, and controlling current using this detected value, thereby improving control properties when motor temperature has increased and lowering cost.
2. Description of the Related Art
FIG. 1 shows a conventional method of this type which has generally been used as a method for driving a servo-motor.
That is, a current command Icmd is input to a calculator 1. The output 1a of the calculator 1 is sent via a proportional and/or integral controller 2 and is input as a voltage command 2a to a power converter 3, comprising a known power element configuration. The power converter 3 supplies a three-phase drive current Iu, Iv, Iw to a servo-motor 4. A current sensor 5 detects one part of the three-phase drive current Iu, Iv, Iw, and the detected current value Ivcc is input to the calculator 1 via an A/D converter 6, thereby forming a current feedback control.
Since the conventional servo-motor driving method has the configuration described above, it has problems such as the following.
That is, a current sensor and an expensive A/D converter are required in order to form the current feedback system, constituting a considerable obstacle to lowering the cost of the control system.